Meat fatty acid composition is of great interest because of its implications for human health. High intake of saturated fatty acids (SFA) can result in elevated plasma cholesterol, which contributes to cardiovascular disease (Bronte-Stewart et al., 1956). Of the SFA, C12:0 (lauric), C14:0, (myristic) and C16:0 (palmitic) are considered to have the most harmful cardiovascular effects (Keys et al., 1974), whereas C18:0 (stearic) is believed to be neutral (Bonanome and Grundy, 1988). In contrast, polyunsaturated fatty acids (PUFA) and MUFA increase hepatic LDL receptor activity, thereby decreasing the circulating concentration of LDL-cholesterol (Woollett et al., 1992; Rudel et al., 1995).
The ruminal microorganisms of beef cattle hydrogenate the majority of dietary unsaturated fatty acids, which results in a higher concentration of saturated fatty acids in beef compared with meat from nonruminant animals. The consumption of beef in the U.S. has decreased from a high of 40.4 kg per capita in 1976 to 29.5 kg per capita in 2003. One of the major concerns that affects beef intake is the high concentration of SFA in beef. For many years, dietitians and health professionals have recommended decreasing or excluding the consumption of foods rich in SFA, such as beef.
Unlike that for nonruminants, the fatty acid composition of beef is much less dependent on the diet. The key lipogenic enzymes in fatty acid synthesis pathways, therefore, play an important role in determination of the fatty acid composition of beef. Fatty acid synthase (FAS) is a multifunctional enzyme complex that catalyzes the synthesis of long-chain SFA. It is a homodimer of two identical subunits that contain seven different catalytic sites, which are β-ketoacyl synthase, malonyl/acetyl transferase, dehydrase, enoyl reductase, β-ketoacyl reductase, acyl carrier protein (ACP), and thioesterase (TE) from N to C terminus. Thioesterase domain in FAS complex is responsible for termination of the fatty acid synthesis and release of newly synthesized SFA, mainly C16:0, (palmitic) by hydrolyzing the acyl-5-phosphopantetheine thioester, which is bound to the preceding ACP domain. Studies have shown that TE has maximal activity for C16-acyl ACP, whereas its specific activity decreases dramatically for chain length longer than C18 or shorter than C16 (Lin and Smith, 1978; Pazirandeh et al., 1989). The TE domain of FAS, therefore, plays an essential role in the determination of the product chain length of FAS. Because the predominant elongation system, which is located in the endoplasmic reticulum (ER) membranes, act on C16 and longer fatty acids (Harwood, 1994), only C16:0 produced by FAS, but not C14:0, can be further elongated and desaturated to form one of the major end product of de novo fatty acid synthesis, C18:1. The product chain length of FAS, therefore, plays a role in determining the fatty acid composition. Therefore, we hypothesized that variation in the TE domain of FAS among individuals would be a candidate for heritable differences in fatty acid composition that might be used to improve the healthfulness of the fatty acid composition of beef while maintaining other positive physical and chemical attributes of the product.
It is an object of the present invention to provide a genetic test for determining the likely fatty acid content of meat animals, primarily bovine.
It is yet another object of the present invention to provide the molecular basis for characterizing and further understanding the fatty acid content in cattle.
It is yet another object of the invention to provide further information for understanding and regulating the role of fatty acid synthase in meat product fatty acid content.
It is yet another object of the present invention to use the above information to identify other mutations in linkage disequilibrium with or that are causative of differences in fatty acid content in specific lines, populations, or breeds of cattle.
Other objects will become apparent from the detailed description of the invention which follows.